The present invention relates to an arrangement of sensors on the landing gear of an aircraft for measuring the weight and position of center of gravity of the aircraft.
In the arrangements of this type which are known in actual practice, there are provided, in particular, inductive sensors of the type having two series-connected coils which are arranged one above the other with a common center line in a first sensor part, and having a tongue of ferromagnetic material which is moveable in the coils and is part of a second sensor part. The first and the second sensor parts are each arranged on one lug of a pair of lugs which protrude at the measurement point from an axle or a bogie beam of an aircraft landing gear. The series-connected coils of the sensor act as inductive voltage divider and each of them gives off a signal if a line of bend of the axle or bogie beam is not curved uniformly and with center symmetry, i.e. symmetric to the center line of a pair of lugs, at the point of measurement. The line of bend is in this connection the neutral line of the elastic body represented by the axle or bogie beam or a line parallel to it. In the ideal case, the sensor measures only the shear, caused by the load introduced into the landing gear, of the axle or bogie beam in the region of the measurement point at which the sensor is arranged.
Differing from the ideal case, one of the possible errors of measurement occurs in the event of torsion and also in the case of additional shear of the landing gear which have been caused not only by the load but, for instance, dynamically upon braking or traveling around curves. This torsion and additional shear of the landing gear, however, do not occur only upon travel, but also upon standing if, for instance, the entire landing gear or individual wheels are not level. In order to compensate for the measurement errors caused at the point of measurement as a result of the torsion of the axle or bogie beam, it is known to arrange one sensor each on a pair of lugs at two measurement points of the axle or bogie beam or of the shock-absorber landing-gear leg which lie opposite each other on the outside. In this way, both of the sensors of this arrangement which lie opposite each other on the outside experience an oppositely directed equal deflection as a result of a moment of torsion which occurs on the axle or bogie beam. The output signals of the two sensors are so linked to each other in an electronic device, particularly a computer, that the effects of the moment of torsion on the two sensors compensate for each other. In actual practice however this compensation is not complete.